The same day this week that Immigration and Customs Enforcement announced the arrests of 245 people accused of exploiting and abusing children, a tip alerted authorities to arrest one more suspect: a woman in Los Angeles whom law enforcement had identified in photos posted online that allegedly show her sexually molesting a girl thought to be 13 years old. The photos date back to 2001 and were discovered by ICE field agents in Chicago in 2007.

Such is the complex effort that goes into pursuing online sexual predators who rely on computer technology to produce and distribute images of their abuse and are becoming more adept at hiding their identities.

Concentrated over a five-week period in November and early December, Operation Sunflower was a “surge operation” in which agents were encouraged to “really get down and look at who is in those photos,” says Danielle Bennett, a spokeswoman for ICE in Washington. The increased effort resulted in finding 123 victims. Of that total, 44 were found living with their abusers and subsequently were removed from the homes. The others were exploited outside their own homes or are now adults.

Law enforcement officials at the federal, state, and local levels have been turning to what they call “forensic technology” to track and identify both predators and their victims. The effort to focus on minute details of photos or videos and rely on global databases to establish trends or locations has yielded more arrests. The number of child predators arrested by ICE last year totaled 1,655, a record number for the agency and an 81 percent increase from 2010.

In Operation Sunflower, whose results were announced Thursday, the majority of the victims were female, and most victims were between 13 and 15 years old. However, five victims were under the age of 3, and 30 were between 4 and 9 years old.

The majority of suspects were arrested in the United States, but 23 were arrested abroad. The states with the most arrests were California (37), Texas (29), New York (19), Florida (17), and New Mexico (11). States with destination theme parks and family-friendly attractions tend to be targets of predators because they usher through a high volume of children each year.

Ms. Bennett says that Homeland Security Investigations (HSI), the unit within ICE pursuing online predators, is now focusing on “victim-centered investigations,” in which the agency tries to track the identities of the victims first instead of predators. Each time an agent uncovers evidence, it is sent to the National Center for Missing & Exploited Children, a partner since last year, to see if it matches similar images from that database.

HSI also relies on advanced software to examine minute details of photos and videos, and it trains agents to understand the shifting behavior of predators.

“As technology gets better ... the bad guys are getting better in using technology to hide themselves. We have to be one step ahead,” says Bennett.

With each arrest, there can be setbacks. For example, the Los Angeles woman arrested, Letha Mae Montemayor, allegedly conducted activities with another adult who remains on the loose. Ms. Montemayor was linked to the photos through her unique tattoos that were registered into a database and were eventually identified by a tipster. The second adult – identified on his federal arrest warrant as “John Doe” – has evaded capture so far because he inserted a black dot over the images of his face, ICE says.

The proliferation of portable media – smart phones, tablets, laptops, as well as the household PC – is making it easier for predators to find, approach, and eventually lure children, says Chuck Williams, director of the Center for the Prevention of School-Aged Violence at Drexel University in Philadelphia.

“These predators are extremely savvy in that they understand the culture of young people. Then they exploit the fact that adults are not anywhere near as vigilant in supervising the behavior as it relates to our young people,” he says. “Which is why they prey on them through these various avenues – they are not policed at all.”

While software exists to allow parents to monitor every message, image, or online posting made on the devices of their children, many parents tend not to pursue such safety measures, Mr. Williams says.

“Parents need to be educated to do more. The front line is the home,” he says.

Bennett agrees: “These kinds of cases remind us we need to have conversations as educators and parents that ask children, ‘When you go online on Facebook, how do you know that person who says he’s Johnny and he’s a 14-year-old is [being honest]?’ ”